1. Technical Field
The present invention relates to an LED lighting device for an aircraft, in particular for maneuvers of landing, and/or take-off, and/or taxiing, and/or searching, to a lighting system comprising a plurality of lighting devices, and to an aircraft comprising said lighting system.
2. Description of the Related Art
As is known, aircraft (for example, airplanes, helicopters, etc.) enabled for night-time operations are obliged to mount a plurality of lighting systems, necessary during operations of take-off and landing (landing lights), taxiing on the runway (taxi lights), and searching (search lights). Said lights can moreover have signaling functions for other aircraft, for the control tower, etc.
Lighting systems used for landing operations are of crucial importance in so far as they perform the function of illuminating the runway during take-off and landing so that the pilots can visually assess the conditions of the runway. Furthermore, in some cases, the same lights can be used by control-tower operators (and possibly by pilots of other aircraft) for visual identification of the presence and/or direction of flight of the aircraft provided with said lighting systems.
Taxi lights are, instead, used when the aircraft is moving around on the ground and have the function of improving visibility for the pilots, above all in airports that are poorly illuminated. Taxi lights are in any case kept on, together with the landing lights, during the operations of take-off and landing to improve further visibility of the runway.
The lighting systems for landing, taxiing, and searching must be configured so as to provide a long-distance lighting (hundreds of meters), and consequently must generate a light beam of a very high intensity. Avionics standards, such as, for example, MIL-L-006730, MIL-L-6503, and SAE ARP 693, require, for landing lighting systems, a value of peak light intensity higher than approximately 300,000 cd, with a beam spread (defined as the angle for which the light intensity decreases to 10% with respect to the peak intensity) of approximately 10°. The aforementioned avionics standards require a peak light intensity for taxi lights higher than approximately 50,000 cd, with a beam spread of approximately 40° in the horizontal plane and 10° in the vertical plane.
To meet the performance requirements, lighting systems of a known type comprise a single incandescent lamp, halogen lamp, or high-intensity discharge (HID) lamp set along the central axis of a cylindrical or hemispherical, or generally parabolic, reflector. Said configuration is rendered necessary by the fact that incandescent, halogen, and HID light sources emit a light beam with a solid angle of approximately 4°; for this reason, the reflector generally has the shape of a paraboloid of revolution, and, consequently, the lighting system as a whole assumes a cylindrical shape with a diameter greater than 10 cm.
Lights that comprise incandescent lamps, halogen lamps, and HID lamps present the disadvantage of having a poor reliability (they last only a few thousand hours), moreover reduced by the marked environmental stresses to which they are subjected during their service life. Consequently, for safety reasons, many aircraft mount a plurality of reserve lighting systems, which cause an increase in weight of the aircraft itself, as well as an increase in the costs of production and maintenance. In addition to the poor reliability, also the consumption of incandescent or halogen lamps is not negligible (several hundred watts).
Given that the ideal position of said lights is typically under the nose of the aircraft, their shape and dimension create friction with the air in flight. For this reason, the lights are frequently equipped with a mechanical system for sending out the lights, which increases the cost of the light as well as the maintenance costs.
It should be borne in mind that the lighting performance required by avionics standards must be guaranteed in all the real conditions in which the aircraft might find itself, hence even at temperatures exceeding 50° C. Furthermore, the performance envisaged by the aforementioned standards is required also when the lighting device is at the end of its service life, after a certain number of operating hours. For these reasons lighting devices for aircraft, at the start of their service life and in conditions of standard operation (typically, at approximately 25° C.), frequently have to be designed to guarantee a lighting intensity that is considerably higher than the theoretical lighting intensity required. A high lighting intensity is a cause of high generation of heat by the light sources themselves, of whatever type they may be. Said heat, if not appropriately dissipated, causes a shortening of the service life of said light sources, or failure thereof. Appropriate heat dissipaters must be consequently provided, at the cost of an increase in the overall dimensions required by the lighting systems and in weight. This is a further problem of lighting systems of a known type.